Copolarized and Cross‐Polarized SAR Measurements for High‐Resolution Description of Major Hurricane Wind Structures: Application to Irma Category 5 Hurricane

Mouche, Alexis; Chapron, Bertrand; Knaff, John A.; Zhao, Yunyan; Zhang, Biao; Combot, Clément

doi:10.1029/2019jc015056

Cited by 83 publications

(59 citation statements)

References 60 publications

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“…The C-band radar's signal was hardly affected by weak rainfall. However, due to the ambiguity of estimating and separating the contributions of precipitation from winds, eliminating intense rain impact on wind retrieval is still a problem [21].…”

Section: Discussionmentioning

confidence: 99%

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Extreme Wind Speeds Retrieval Using Sentinel-1 IW Mode SAR Data

et al. 2021

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With the improvement in microwave radar technology, spaceborne synthetic aperture radar (SAR) is widely used to observe the tropical cyclone (TC) wind field. Based on European Space Agency Sentinel-1 Interferometric Wide swath (IW) mode imagery, this paper evaluates the correlation between vertical transmitting–horizontal receiving (VH) polarization signals and extreme ocean surface wind speeds (>40 m/s) under strong TC conditions. A geophysical model function (GMF) Sentinel-1 IW mode wind retrieval model after noise removal (S1IW.NR) was proposed, according to the SAR images of nine TCs and collocated stepped frequency microwave radiometer (SFMR) and soil moisture active passive (SMAP) radiometer wind speed measurements. Through curve fitting and regression correction, the new GMF exploits the relationships between VH-polarization normalized radar cross section, incident angle, and wind speed in each sub-swath and covers wind speeds up to 74 m/s. Based on collocated SAR and SFMR measurements of four TCs, the new GMF was validated in the wind speed range from 2 to 53 m/s. Results show that the correlation coefficient, bias, and root mean squared error were 0.89, −0.89 m/s, and 4.13 m/s, respectively, indicating that extreme winds can be retrieved accurately by the new model. In addition, we investigated the relationship between the S1IW.NR wind retrieval bias and the SFMR-measured rain rate. The S1IW.NR model tended to overestimate wind speeds under high rain rates.

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Section: Discussionmentioning

confidence: 99%

“…Lat1 and Lon1 are the latitude and longitude of external matching point after shift. In wind retrieval research, the location shift has been proven to be beneficial to collocation and comparison [21]. SAR images were matched with wind references consistent in time and space.…”

Section: Data Collocationmentioning

confidence: 99%

Extreme Wind Speeds Retrieval Using Sentinel-1 IW Mode SAR Data

et al. 2021

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“…Studies have shown that C-band co-and cross-polarized SAR observations can be used to retrieve accurate TC wind fields [24][25][26][27]; the root-mean-square error (RMSE) is about 5 m/s for wind speeds up to 75 m/s compared to the collocated SFMR observations [27]. Moreover, TC centers, radii of maximum wind speed, and the azimuthal wave-number one asymmetry of surface winds have been studied using cross-polarized SAR images [28]. A recent study has shown that SAR-derived highresolution TC wind fields can be used to estimate parameters related to TC wind structure [27].…”

Section: Introductionmentioning

confidence: 99%

Estimating Tropical Cyclone Wind Structure and Intensity From Spaceborne Radiometer and Synthetic Aperture Radar

Zhang

Zhu

Perrie

et al. 2021

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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We present a relatively simple method to estimate tropical cyclone (TC) surface wind structure (34-, 50-and 64-kt wind radii) and intensity (maximum wind speed, MWS) from wind fields acquired from the L-band SMAP radiometer and C-band Sentinel-1A/B and RADARSAT-2 synthetic aperture radar (SAR) between 2015 and 2020. The radiometer and SAR-derived wind radii and MWS are systematically compared with the best-track estimates. The root-mean-square errors (RMSEs) of R34, R50 and R64 are 31.2, 21.8 and 17.0 n mi (1 n mi =1.852 km) for radiometer, and 21.7, 16.5 and 16.3 n mi for SAR, respectively. These error values are smaller than the averaged best-track uncertainty estimates for the three wind radii. Compared to best-track reports, the bias and RMSE for the MWS estimates are-0.2 m/s and 5.8 m/s for radiometer, and 4.4 m/s and 9.1 m/s for SAR, respectively. These results are for the wind speeds in the range of 17-80 m/s. For the two typical TCs (Lionrock and Noru) in the Northwest Pacific Ocean, our results show that a combination of the radiometer and SAR wind data acquired within a very short time interval has the potential to simultaneously obtain reasonable measurements of the wind radii and intensity parameters. Moreover, for a TC with long lifecycle, such as Typhoon Noru, we demonstrate that high-resolution and multi-temporal synergistic observations from SAR and radiometer are valuable for studying fine-scale features of the wind field and characteristics of wind asymmetry associated with intensity change, as well as the evolution of TC surface wind structure and intensity.

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“…With the development of remote sensing technology, using radar observation to obtain typhoon wind field information has become an effective method. Synthetic aperture radar (SAR) is unique to probe the sea surface at very high resolution under extreme weather conditions [3]. Compared to the remotely sensed winds derived by microwave scatterometers or radiometers observations, the SAR-derived wind product usually has a much higher spatial resolution to obtain the detailed distribution of hurricane winds, which is useful for capturing the structural characteristics of hurricanes, such as the eye and eyewall.…”

mentioning

confidence: 99%

“…Based on these new findings, several cross-polarized empirical GMFs have been established [9][10][11][12][13][14][15][16]. When coanalyzed with airborne Stepped Frequency Microwave Radiometer (SFMR) wind estimates, the radar backscatter signals acquired in major hurricanes from SAR reveal high sensitivity in the cross-polarized channel for wind speeds up to 75 m/s [3]. This makes the cross-polarization SAR a unique tool in hurricane monitoring.…”

mentioning

confidence: 99%